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Consider the following Java program. Which one of the following is an interface?
import java.awt.event.*;
import javax.swing.*;
public class MouseWhisperer extends JFrame implements MouseListener {
MouseWhisperer() {
super("COME CLOSER");
setSize(300,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
addMouseListener(this);
setVisible(true);
}
public void mouseClicked(MouseEvent e) { setTitle("OUCH"); }
public void mousePressed(MouseEvent e) { setTitle("LET GO"); }
public void mouseReleased(MouseEvent e) { setTitle("WHEW"); }
public void mouseEntered(MouseEvent e) { setTitle("I SEE YOU"); }
public void mouseExited(MouseEvent e) { setTitle("COME CLOSER"); }
public static void main(String[] args) { new MouseWhisperer(); }
}
Select one:
a. java.awt.event
b. JFrame
c. MouseEvent
d. MouseListener
e. this
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Your answer is correct.
See Section 6.3.1.
The correct answer is: MouseListener
, Question 2
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Consider the following Java program. What is the superclass of "Clicker"?
import java.awt.event.*;
import javax.swing.*;
public class Clicker extends JFrame implements ActionListener {
int count;
JButton button;
Clicker() {
super("Click Me");
button = new JButton(String.valueOf(count));
add(button);
button.addActionListener(this);
setSize(200,100);
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
setVisible(true);
}
public void actionPerformed(ActionEvent e) {
count++;
button.setText(String.valueOf(count));
}
public static void main(String[] args) { new Clicker(); }
}
Select one:
a. ActionEvent
b. ActionListener
c. JButton
d. JFrame
e. this
Feedback
Your answer is correct.
See Section 5.5.2.